一种基于蜜蜂进化选择算子的布局遗传算法

三维矩形布局问题属于NP难问题,对于三维矩形布局问题的求解大多依赖于各种启发式算法.该文以布局物体体积递减为定序规则,结合布局物体在布局空间中的几何可行域,以吸引子法为定位规则,利用蜜蜂进化型遗传算法优化吸引子函数中的参数来求解三维矩形布局问题（BEGA）,得到新型布局遗传算法.最后对不同的算例进行了计算,并与以标准比例选择作为选择算子的传统布局遗传算法（SPGA）等对比证明了该算法的有效性.     

Markov迭代函数系统分形的动力学特性分析

研究Markov迭代函数系统(MIFS)的转移概率矩阵与MIFS吸引子分形结构之间的关系.首先提出了分支Markov迭代函数系统的概念并将MIFS系统分解成若干分支系统,给出和证明了几个相关定理.然后讨论转移概率矩阵的零元素对吸引子结构的影响,分析吸引子的局部结构特征,发现MIFS系统吸引子包含自相似结构,基于计算机数学实验分析了吸引子分形形成的动力学特性并给予具体的定性描述.     

扇形子孔径布局H-S传感器对圆域的探测性能研究

通过Zernike模式波前重构算法进行计算机仿真计算,对扇形子孔径布局的Hartmann-Shack波前传感器探测性能进行仿真研究,对比分析了方形子孔径布局Hartmann-Shack波前传感器的探测性能.结果表明,扇形子孔径布局是一种有效的Hartmann-Shack波前传感器的布局方式,在低子孔径密度且径数目差异不多的条件下,比方形孔径布局探测精度更高.     

随机敏感度函数法在非自治非线性系统中的应用

研究非自治微分动力系统周期吸引子受弱高斯白噪声扰动后的分布特性。基于频闪映射将微分动力系统离散为映射,通过求解映射系统周期吸引子的随机敏感度函数,构造置信椭圆来刻画随机吸引子的分布情况,从而避免了求解矩阵微分方程的边值问题,只需求解矩阵代数方程即可。研究了Duffing方程随机周期吸引子的分布情况,结果表明置信椭圆与Monte-Carlo模拟取得了很好的一致。最后对Duffing方程的噪声诱导混沌现象进行了定性研究,证明了通过随机敏感度函数可以揭示这类现象的机理。     

一类碰撞振动系统的激变和拟周期-拟周期阵发性

研究了一类三自由度碰撞振动系统的激变和阵发性。六维庞加莱(Poincaré)映射能够表示成另外一个不对称映射的二次迭代,这表明系统具有对称性。该系统普遍存在发生Hopf分岔后得到的一对共轭拟周期运动。根据动力系统的极限集理论,讨论了极限集的对称性,得到系统发生激变的条件,并引入一个距离函数判定对称性恢复和激变临界点。当共轭混沌吸引子和不稳定对称不动点的最小距离等于0时,一对共轭混沌吸引子将会与不稳定的对称不动点在其吸引域边界发生碰撞,从而导致激变。通过数值模拟,揭示了激变之后的一种新的阵发性动力学现象:拟周期-拟周期阵发性。其分岔机制是:两个共轭拟周期吸引子→两个共轭拟周期吸引子倍化→两个共轭带状混沌吸引子→一个对称混沌吸引子→一个对称拟周期引子,通过对称极限集理论来区分对称吸引子和共轭吸引子,同时采用QR法计算Lyapunov指数并用来确定吸引子的类型。激变导致的拟周期-拟周期阵发性,对于多自由度碰撞振动系统的动力学研究及优化设计具有重要意义。     

IFS吸引子的界与其动力学性态的研究

阐述了迭代函数系(IteratedFunctionSystem,简称IFS)理论及随机迭代算法,通过理论解析给出了求IFS吸引子界的方法,介绍了IFS吸引子的Lyapunov指数和关联维数的算法。利用计算机构造了一系列IFS吸引子,计算了IFS吸引子的界、Lyapunov指数和关联维数,分析了IFS吸引子的动力学特征,讨论了当参数变化时IFS吸引子界的变化规律。     

一种带自动参量的迭代函数系统

迭代函数系统(IFS)是生成分形吸引子的经典方法。基于IFS理论研究了系统的控制参数可以随计算程序的迭代过程不断自动变化的情况,在原有系统的迭代码中,通过嵌入不同形式的函数对原有系统进行改造,拓宽了系统的参数调控范围。实验表明,利用推广后的系统能构造大量造型新颖的吸引子图像。     

IFS分形吸引子控制技术综述

迭代函数系统(IFS)是分形吸引子生成的典型方法,近几年来其研究取得了较大的进展,但吸引子的控制技术还很不成熟.概述了国内外的最新研究结果,分析了参数控制、仿射变换控制、概率分布控制和图形交互操作控制等方法,比较了各种控制方法的优缺点.最后指出IFS分形控制技术目前存在的问题和进一步的发展方向.     

求解矩形布局问题的自适应算法

矩形布局问题属于NP-Hard问题,其求解算法多为启发式算法。该文侧重于构造布局求解算法中定位函数(规则)的优化,将模拟退火算法的思想融入到遗传算法中,提出了求解矩形布局问题的自适应算法,其利用自适应交叉、变异及接收劣质解的概率等方法对定位函数中各参数进行优化。算法通过两种方式确定初始种群的数目,具有较强的适应性。在算法搜索的后期,利用差异性较大的个体进行交叉操作,从而保持种群的多样性。最后通过实例证明了该算法能够很好的应用于矩形布局问题的求解。     

求解对称锥互补问题的一种非精确光滑牛顿方法(英文)

本文给出了一种求解对称锥互补问题的非精确光滑牛顿方法,所采用的互补函数是含一个参数且以FB和CHKS为特例的光滑函数.新方法的每步迭代中,都采用非精确牛顿方法求解由原问题产生的子问题.在一定条件下,新算法具有全局收敛和局部超线性收敛的性质.数值试验表明算法对于求解大规模对称锥互补问题是非常有效的.     

Analysis of the plastic zone of a circle crack under very high cycle fatigue

Metals used in industry for structures and aero-engine components are sometimes subjected to very high cycle fatigue (VHCF) damage during their working service. In this paper, a novel method is presented to determine the size and location of a circular crack located within a metal specimen under 20 kHz VHCF loading conditions. The method is based on an analysis of the temperature rise on the surface of the specimen and correlation of this temperature rise to the energy dissipation in the plastic zone of the crack. The approach taken is to first determine the heat source location and strength using an inverse heat transfer calculation based on the surface temperature measurements. Next, the relationship between the heat and the material hysteresis loop in the plastic zone, which is a function of stress intensity factor and vibration amplitude cyclic loading of the specimen, is found. The calculation of the stress intensity factor under vibrational loading is often an obstacle in VHCF research because there is currently no standard or existing formula. In this paper a general polynomial formula for the stress intensity factory under 20 kHz loading conditions is obtained using a finite element modeling approach as a function of the specimen’s material properties and position and size of the internal crack.     

Exploring the interatomic forces between tip and single molecules during STM manipulation

The interaction between a single molecule and the STM tip during intramolecular manipulation is investigated in detail. We show that the conformational change of complex organic molecules can be induced reversibly and very reliably by using exclusively attractive forces. By studying the dependence of this process on the bias voltage and the tip position, the driving forces are characterized. Different regimes of tip-molecule interactions are observed as a function of the distance.     

A simulation-based optimization approach to size manufacturing systems

The problem of sizing the resources of a production system is widely encountered both in the literature and in practice. Simulation is a very useful method to identify the necessary number of resources. However, if there are numerous resources, it can become impossible to make a sound ‘trial-and-error’ analysis with simulation models, so that strategies using simulation optimization appear as an attractive approach. Unfortunately, it is necessary to specify a cost function, and, in practice, it is often very difficult to formalize such a function which is used to determine the number of resources that will minimize this cost. In this article, we propose a different modelling approach, which aims at sizing the resources so as to meet the design specifications. In this respect, we search for the minimum number of resources of each type, while satisfying the performance requirements specified in the design project. As a result, the problem is formulated as a stochastic multi-objective optimization problem with constraints. The approach used here is based on simulation, used in conjunction with a bootstrap approach which accounts for the stochastic aspect of the model, and with regression metamodelling in order to derive an analytical formulation of the constraints together. Different multi-objective optimization methods can then be used to solve the problem. An illustrative example is given.     

Development of a New Alpha Function for the Peng–Robinson Equation of State: Comparative Study of Alpha Function Models for Pure Gases (Natural Gas Components) and Water-Gas Systems

Numerous modifications have been suggested for the temperature dependence of the attractive term of the Peng–Robinson equation of state (PR-EOS), through the alpha function. In this work, a new alpha function combining both exponential and polynomial forms is proposed. Pure-compound vapor pressures for different molecular species were fitted and compared using different alpha functions including the Mathias–Copeman and Trebble–Bishnoi alpha functions. The new alpha function allows significant improvements of pure compound vapor pressure predictions (about 1.2% absolute average percent deviations) for all the systems considered, starting from a reduced temperature of 0.4. In addition, a generalization of the classical Mathias–Copeman alpha function was proposed as a function of the acentric factor. These alpha functions were used for VLE calculations on water+various gases including gaseous hydrocarbons. A general procedure is presented to fit experimental VLE data. The corresponding thermodynamic approach is based on the Peng–Robinson equation of state with the above cited alpha functions. It includes the classical mixing rules for the vapor phase and a Henry's law approach to treat the aqueous phase.     

Attractive regions formed by the environment in configuration space: The possibility of achieving high precision sensorless manipulation in production

One of the main purposes in robotic manipulation is to eliminate the uncertainty in the location of objects. So far, the controller system with sensory feedback has been used in most dynamic systems to eliminate the uncertainty of the system state. However, sensorless manipulation can also eliminate the uncertainty of the system state, which avoids problems caused by sensors. Recently, the approach on sensorless manipulation has drawn increasing attention and many important results have been presented. However, in general, it is believed that sensorless manipulation can only achieve low-precision or simple tasks that are greatly limited in their application areas. Stimulated by work in related areas, an interesting concept of 'attractive region in configuration space' was proposed. Through a unique method of formulation and utilization of the attractive region in the configuration space, (1) the strategy to achieve high-precision assembly in 3D without a force sensor and a flexible wrist was designed directly and (2) the available initial region from which an object can be grasped into a stable state with a certain gripper was obtained directly. These show that the strategy to achieve high-precision sensorless manipulation can be formed systematically through the formulation and utilization of attractive regions in configuration space, if the strategy exists. The work may also include the approaches on 'how to find the maximum attractive region' and 'when the attractive region exists'.     

Analysis of geometrical error in the stereolithography process using a stochastic approach

The geometrical error in the stereolithography process is analysed using a stochastic approach. This approach is based on a unified methodology, developed by the authors, for studying the mechanical error in different rapid prototyping processes. The tolerances and clearances have been assumed to be random variables. The coordinates of a point on the resin surface, traced by the laser beam, are expressed as a function of random variables. In a numerical example, the geometrical error has been found for a grid of points traced by the laser beam. The three-sigma error bands are plotted when tracing example curves. This is the band in which the laser beams of 99.73% of machines, produced on a mass scale, lie on the work surface for the given tolerances and clearances. Stringent values of tolerances and clearances reduce the error at the tool tip, but the cost of manufacturing and assembling the machines may become prohibitive.     

Spatial Micropatterning of Growth Factors in 3D Hydrogels for Location‐Specific Regulation of Cellular Behaviors

Growth factors are potent stimuli for regulating cell function in tissue engineering strategies, but spatially patterning their presentation in 3D in a facile manner using a single material is challenging. Micropatterning is an attractive tool to modulate the cellular microenvironment with various biochemical and physical cues and study their effects on stem cell behaviors. Implementing heparin's ability to immobilize growth factors, dual‐crosslinkable alginate hydrogels are micropatterned in 3D with photocrosslinkable heparin substrates with various geometries and micropattern sizes, and their capability to establish 3D micropatterns of growth factors within the hydrogels is confirmed. This 3D micropatterning method could be applied to various heparin binding growth factors, such as fibroblast growth factor‐2, vascular endothelial growth factor, transforming growth factor‐betas and bone morphogenetic proteins while retaining the hydrogel's natural degradability and cytocompability. Stem cells encapsulated within these micropatterned hydrogels have exhibited spatially localized growth and differentiation responses corresponding to various growth factor patterns, demonstrating the versatility of the approach in controlling stem cell behavior for tissue engineering and regenerative medicine applications.     

Methods to detect objects in photon-limited images

We investigate the problem of detecting and localizing a known signal in a photon-limited image, where Poisson noise is the dominant source of image degradation. For this purpose we developed and evaluated three new algorithms. The first two are based on the impulse restoration (IR) principle and the third is based on the generalized likelihood ratio test (GLRT). In the IR approach, the problem is formulated as one of restoring a delta function at the location of the desired object. In the GLRT approach, which is a well-known variation on the optimal likelihood ratio test, the problem is formulated as a hypothesis testing problem, in which the unknown background intensity of the image and the intensity scale of the object are obtained by maximum-likelihood estimation. We used Monte Carlo simulations and localization receiver operating characteristic (LROC) curves to evaluate the proposed algorithms quantitatively. LROC curves demonstrate the ability of an algorithm to detect and locate objects in a scene correctly. Our simulations demonstrate that the GLRT approach is superior to all other tested algorithms.     

A TDR Method for Real-Time Monitoring of Liquids

Time-domain-reflectometry (TDR) measurements, which were originally used to locate and diagnose faults in transmission lines, have been widely applied in geology and soil science for accurate and flexible measurements of soil moisture and water content. Furthermore, the most attractive advantages of TDR rely on the possible determination of the spatial location and nature of various objects, both in real time and with a nondestructive approach. This makes the TDR technique an appealing candidate for a variety of environmental and industrial applications. Although the TDR instruments are commonly used to date, particularly for the aforementioned purposes, the state of the art is rather lacking in liquid-monitoring applications. This paper describes how the suitable combination of TDR detecting functionalities can lead to a simultaneous monitoring of quantitative and qualitative properties of liquid samples. In fact, the proposed TDR method allows, in one shot, the measurement of liquid levels, the determination of multiple interfaces in layered media, and the evaluation of dielectric properties such as dielectric permittivity or electrical conductivity. Some applications to real cases are proposed, which are referred to petrol-chemical mixtures or water-based liquids, thus validating the approach on a wide range of materials.     

An iterated IRS technique for cross-sectional damage modelling and identification in beams using limited sensors measurement

This paper presents an effective method for cross-sectional damage localization and quantification in beams. First, a new strategy is suggested for cross-sectional damage modelling by means of Iterated Improved Reduction System (IIRS) approach. Then, a novel damage localization index is proposed employing Grey System Theory (GST) as a geometrical criterion for quantifying the amount of correlation between vectors of the calculated curvatures for the diagonal members of the flexibility matrices in the damaged and undamaged states. Since the method employs only the modal data of the translational degrees of freedom, it can be interpreted as damage identification method by utilizing incomplete modal data or installing a limited number of sensors. After detecting the damage location, to estimate the exact parameters of the cross-sectional damage, the problem is defined as a finite element model-updating problem which is solved with a new evolutionary optimization approach named Imperialist Competitive Algorithm (ICA). The applicability of the method is demonstrated by studying different damage patterns on two numerical examples of beams. In addition, its robustness is investigated in the presence of random noises and modelling errors. Obtained results emphasize the high accuracy and promising performance of the method, especially when noisy incomplete modal data are used.